Fix copy function and remove slow recursive conversion of newly added nested dict objects

[codecov-commenter]

Codecov Report

Base: 97.70% // Head: 97.66% // Decreases project coverage by -0.04% :warning:

Coverage data is based on head (b52a71f) compared to base (12ec382). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7 +/- ## ========================================== - Coverage 97.70% 97.66% -0.05% ========================================== Files 3 3 Lines 174 171 -3 ========================================== - Hits 170 167 -3 Misses 4 4 ``` | [Impacted Files](https://codecov.io/gh/LarsHill/metadict/pull/7?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Lars+Hillebrand) | Coverage Δ | | |---|---|---| | [metadict/metadict.py](https://codecov.io/gh/LarsHill/metadict/pull/7/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Lars+Hillebrand#diff-bWV0YWRpY3QvbWV0YWRpY3QucHk=) | `97.45% <ø> (-0.05%)` | :arrow_down: | | [metadict/\_\_about\_\_.py](https://codecov.io/gh/LarsHill/metadict/pull/7/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Lars+Hillebrand#diff-bWV0YWRpY3QvX19hYm91dF9fLnB5) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Lars+Hillebrand). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Lars+Hillebrand)

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